It is well known that various communication systems employ more than one frequency band when transmitting electromagnetic or microwave signals from a transmitting station to a receiving station. A typical example of such a communication system is a satellite communication system wherein various bands of signals are transmitted between a satellite above the earth (geosynchronous orbit) and ground stations on the earth. Two such frequency bands of interest herein include the Ka band of 20 GHZ, which ranges from 19.7 to 20.2 GHZ, and the Ku band of 12 GHZ, which ranges between 11.7 to 12.7 GHZ.
Historically, the practice has been to provide separate antennas for transmission or reception of each of the bands because there is insufficient band width on any one of the antenna systems or terminals to transmit more than one of the bands. In some cases, where bands are close together and, collectively, do not occupy an excess amount of spectral space, it has been possible to share a plurality of bands on one antenna. However, separate antennas have been employed for different portions of the spectrum.
Microwave multiplexers have been developed and utilized in communication systems, such as satellite communication systems, for combining numerous signal channels for transmission along a common transmission path, such as an antenna feed. In a frequently employed form of satellite communication system, an antenna carried by a satellite transmits and/or receives electromagnetic signals propagating between a satellite and an antenna located on the earth's surface. Plural signal channels separated by frequency and/or by polarization are communicated by the two antennas. It is important that the signals of all the channels, whether they are literally polarized or circularly polarized, propagate along the same path in a common direction so that all of the signals transmitted by a transmitting antenna reach a receiving antenna.
While such multiplexers have been employed in both land-based and in satellite communication systems, problems arise in that multiplexers are typically complex and heavy in their mechanical structure. Such multiplexers are typically designed for low-volume, high-performance systems, but the manufacturing costs are prohibitive for high-volume, low-cost components. Therefore, it would be desirable to provide a simple, lightweight, and inexpensive diplexer that could accommodate various frequencies and polarities.